A seal ring that is made of a hard material such as a resin or metal is provided with an abutment joint for absorbing a difference in linear expansion. The abutment joint is a separated part in the circumferential direction in the seal ring. When being in the free length of the seal ring in a no-load condition, the opposite ends of the seal ring, the opposite ends forming the abutment joint, are separated from each other in the circumferential direction, and the outer diameter dimension of the seal ring is slightly larger than the inner diameter dimension of an assembled object (e.g., a nozzle). When the seal ring is assembled to the inside of an inner wall of the assembled object, the outer peripheral edge of the seal ring is pressed against the inner wall of the assembled object, and the outer peripheral edge of the seal ring fits with the inner wall of the assembled object.
The opposite ends of the seal ring, the opposite ends forming the abutment joint, may not be aligned, but may be displaced from each other in the radial direction due to a local load applied to the seal ring when a valve is opened or due to distortion that occurs in the seal ring. In order to prevent the displacement, there has been proposed a seal ring provided with a step cut joint that prevents a displacement in an abutment joint in the radial direction by engaging the ends of the seal ring, the ends forming the abutment joint, with each other in the radial direction (e.g., refer to Patent Literature 1). However, in the configuration of Patent Literature 1, there is an apprehension that a gap may be formed in the abutment joint, and fluid may leak through the gap.